French Door Security

Last Updated on July 14, 2023

How to Better Secure French Doors

French doors are one of the weakest security points in your home due to two individual doors meeting in the middle. When they are not properly locked, or the locks provided during the installation have not been modified, these doors can be made to easily swing open even when the deadbolt and door lever have been locked.

French Door Terminology

For the best French door security: 1) Install a screw that prevents the unlocking of the passive door, 2) Install security film to protect the glass from being broken out, 3)Install new locks that join both sides of the door together so that they cannot be separated by swinging both sides open at the same time.

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Quick Answers to Common French Door Security Questions

No. French doors have a major security flaw that needs to be addressed.
No. There is an easy fix for weakest point that costs less than $1 to fix. From there, as you add security, cost can go up depending on the level of security.
Possibly. There are two ways to prevent this. You can stop the glass from being broken using security window film. Or, you can install a double deadbolt so if broken, the door still cannot be unlocked.
If you are protecting extreme valuables, doing everything we recommend will make that security one of the strongest security points in your home.

Are Double Doors Safe?

French doors, or double doors, are composed of two doors that meet in the middle. One door is referred to as the passive door. This is the door that is seldom used. The other door is referred to as the active door. This is the side that is normally opened and closed.

French doors suffer from the same security weaknesses as any exterior door in the home. We have written an article on How to Reinforce an Entry Door in 6 Easy Steps. Everything in that article applies here as well.

Securing Passive Door
Slide Bolt or Flush Bolt for Securing the Passive Door

But French Doors also have specific security concerns that make them more vulnerable to burglary than a standard door. Once you’ve addressed the specific double-door security weaknesses here, take a look at the above article to make sure that all your doors are reinforced.

The specific security weakness of a French door comes from the fact that the two doors meet in the middle. Because the passive side of the door is seldom used, it is secured into the top and bottom of the door frame. Most commonly this is done using flush bolts installed in the edge of the passive door (see photo).

The active door is then locked in place, by locking it into the secured passive side of the door via a deadbolt. This method of securing double doors is the most common used and relies heavily on the passive side of the door being secure at all times.

Should the passive side of the door not be secured to the door frame, the two doors can simply be pushed open without any resistance, even though the deadbolt of the active side is locked into the passive side it will just slide out as the two doors are pulled open. The photo below illustrates this point. It is viewed as if looking down on the door from the top.

The French Door Security Flaw

The Biggest Security Flaw of French Doors

A Screwdriver Can Unlock the Flush Bolt

As long as the passive door remains secure to the door’s frame, then there should be no problem.

However, the passive side of the door can easily be unlocked. There are numerous YouTube videos showing a variety of techniques to unlock a double door. All it really takes is a thin screwdriver, drywall hammer, or even a heavy coat hanger to bypass the door locks.

If you position any thin, rigid device into the seam between two doors, you can use it to latch the flush bolt, and then slide it to the unlocked position. It takes just a few seconds to open double doors using this technique.

Important: Your secured double door can be unlocked, in just a few seconds, with no visible signs of forced entry, using the above method.

We see a lot of French doors installed near our Scottsdale location and Gilbert lock shops that have newer and higher end homes. Our Tempe service also sees a lot of them because they are a college town and have lots of condos that have them.

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How to Secure French Doors – Quick and Easy Solution

We’ll discuss a couple of ways to secure your French door, but this technique is the simplest, cheapest and easiest. It won’t address any other security weakness of the double door (such as the glass), but it will prevent someone from getting into your double doors undetected as we’ve just discussed. All it takes to prevent this bypass, is a single screw.

Using a screw to lock the flush bolt.
Insert Screw into Flush Bolt

The passive side of the door is very seldom used. Most homeowners only unlock it and use it when they are trying to get something very large into or out of the house.

Keeping that in mind, we recommend screwing screws into each flush bolt so that they cannot be slid open until the screws are removed.

This simple, cheap, DIY, double-door security improvement will prevent the above mentioned home break-in technique 100%.

To do this, slide the flush bolt into the door’s frame, securing the door. Then screw a small screw into the bottom of the flush bolt so that the bolt can not be opened until the screw is removed.

If at some point, you need this door, simply remove the screws, and then reinstall them when you no longer need to use that side of the door.

This technique, combined with the How to Reinforce an Entry Door in 6 Easy Steps, will make your double doors as secure as any door or window in the house.

But what if you want more security? You can go further by preventing the glass in the door from being shattered, buy reinforcing the door and/or by installing high security locks.

Glass Door Security Window Film

Security Window Film Prevents Window Breakage
Security Window Film, at Home Depot

Glass security window film has come a long way. A DIY installation of glass security film is now easily performed by most home owners and the security film will greatly enhance the security of a French door by preventing the glass from being easily broken in order to unlock the door.

Security window film is a film that is attached to the glass. This film is several millimeters thick but clear so that the beauty of the door is not diminished.

When applied to the glass, it acts to hold the glass together so that when the glass is hit, it will not break out. The glass does actually break, but the film holds it together in place.

For best installation of the security window film, remove the panel, install the film, and replace the panel into the window. When this is not possible, we use a thin bead of clear silicon around the edge of the window.

Security film is available for order at Home Depot.


High Security Double Door Locks

When I have customers with large valuables in the home, and double doors, we often increase the security of the French door to the highest level possible. To do this, we:

  1. Install a double side, high security deadbolt into the active side of the French door.
  2. Add one-side half deadbolts to the top and bottom of each door.
The Mul-t-Lock Ball Bearing Locks the Latch and the Strike Together.

High Security Deadbolt Keeps Double Doors Together

When it comes to high security Mul-t-lock is our favorite brand. We discuss it in our online article, Best Lock Brands.

The Mul-t-lock has a feature here that is ideal for double doors. In a Mul-t-lock lock, there is a ball bearing in the bolt that will secure and lock into the strike of the other door. This makes the two doors very difficult to pull apart!

If you are investing in a Mul-t-Lock (check out the prices on Amazon) for a double French door, you do not want to get one with a thumb turn on the inside of the home. Buy a double cylinder deadbolt that takes a key on both sides. This way, if the glass is broken out, the deadbolt cannot be opened using the thumb turn.

Even if you are not spending the additional money on a Mul-t-lock, high security lock for your double door, you should at least upgrade the lock to a commercial grade double cylinder deadbolt for improved security. Our favorite is the Schlage 562 series.

If you order on on Amazon, just take it into your local locksmith so they can key it to your existing house key before you install it. You will need existing Schlage, Emtek, or Dexter door hardware to key this lock to your exiting house key.

If you’re not sure of your options, just call your local locksmith, and they’ll be ready to help.

Really Secure the Passive Door

Half Deadbolt Installed on French Door

Another big boost in French door security comes from eliminating the flush bolt. One of our favorite home locks is the one-sided or “half” deadbolt. This deadbolt has a thumb turn on the inside of the home, but no indication (no keyhole) on the outside of the home. That is, there is no way to tell from the outside of the home that a deadbolt is installed.

We install these at the top and bottom of both double doors. When combined with window security film and an interlocking Mul-t-lock deadbolt, your double door is virtually impenetrable. You will also not need to unscrew screws in order to have access through the passive door; you just unlock the deadbolt using the thumb turn.

Home Depot sells our favorite half deadbolt (the Schlage B80 on Amazon) for less than $25 at the time of this article.

To install them though, you will need to drill holes into both your doors for the deadbolts and the door frame to prep for the latch. This is beyond the skill of most DIYers. So we recommend calling a locksmith in your local area.

French Door, Double Door Reinforcement Kit

In the beginning of this article we touched on the How to Reinforce an Entry Door in 6 Easy Steps article. Again, all the same security tips for any entry door also apply for your French door security.


There is one notable difference, that of the door reinforcement kit. That article discusses the door reinforcement kit (watch me install a door reinforcement kit on our YouTube video).

If you want to reinforce a double entry door, you will need a special door reinforcement kit to do that. At the time of this writing, they were not available on Amazon anymore. The good news is that they are very reasonably priced direct from Door Armor, costing only a few dollars more than the standard door kit.

The kits come with everything needed to reinforce the jam, the door edge, and the hinges. They also come with 3″ screws so you don’t need to secure your French door with those tiny 1/2″ screws.

Getting the Best French Door Security – Summary

Securing your double French doors from the easiest bypass technique can be achieved for practically nothing by adding just one screw.

But if you have high valuables and you want to secure the French door as much a possible, numerous additional things can be done to beef up the integrity of the door to its highest security level, including installing of a lock that stops the doors from being separated.

Which you choose depends on your desired level of security and budget.

Disclosure: As an Amazon / Google / eBay / Home Depot Associate I may earn from qualifying purchases.

More of Our Favorite Security Products

See our Amazon Store for Videos and Links to All of Our Favorite Security Products.

Door Armor: Reinforce your doors. This video on YouTube shows the installation of Door Armor, and you can buy the product direct from Door Armor at a great price.

Video Doorbells: This video doorbell offers great images and video and has NO monthly video storage fees. Watch our SkyBell Video Doorbell Review on YouTube and buy it on Amazon.

Smart Locks: Access Your Locks via Smart Phone. You’ll find some of our favorite smart locks that allow you to control home access and monitor entry in our Amazon Smart Lock Shop. Watch our Smart Lock Comparison Video on YouTube fore reviews of the most popular Smart Locks.

High Security Safes: When you want a safe that is designed to protect the valuable you put inside, you want a high security safe found on ACME Locksmith’s Safes for Sale website.

Sliding Glass Door Lock: The best arcadia door lock that stops your sliding glass door from being lifted out of it’s tracks and to prevent little ones from opening the door and leaving the home. Check out the video on YouTube and Buy it on our website.

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